My 2003 Hyundai Elantra was running just fine. Tonight, I was sitting in my car with the engine off listening to the radio for a few minutes. When I turned the key to the start position, there was a click and all lights turned off. Then, silence. After a bit, the lights would come back on normally, until I turned the key to "start" again.

Internet searches suggested that the problem could be a bad/corroded connection between the battery and a battery cable. So, I ran tests with a volt meter:

Testing the voltage across the battery terminals consistently read about 12 volts, regardless of what I did.

Touching the voltmeter probes to exposed parts of the battery cables produced the following results:

When the lights were working normally, the voltage was about 14 (by my old defective multimeter; I don't have a reading on this from my new meter).

Opening the driver door caused the voltage to drop to nearly zero, then recover to around 1.5.

Attempting to start the car with the lights working normally caused the voltage to drop to nearly 0, then recover to around 1.5. Further attempts to start the car had no effect until the lights started working again.

Because several sources suggested a bad connection between the battery cables and the terminals, I disconnected and inspected them. This battery is nearly new. Upon inspection, I found no evidence of corrosion or a loose connection, and the terminal grease was still intact.

I'm mystified as to how such a problem could crop suddenly with no prior warning. Any ideas as to what I should try?

By the way, my symptoms are basically the same as this question, but as the answers there don't appear to solve my problem, I'm asking my own question.

Edit

I switched multimeters after determining that the one I previously used was giving incorrect readings, and I've edited my post with updated numbers.

It's good that the connections at the terminals are clean and solid. Did you check that the ground cable from the battery is secured on the engine block or appropriate ground location? 18 volts on a 12 volt battery?
– fred_dot_uOct 11 '18 at 9:38

That raised my eyebrow also, 18volts ? What size is your battery, you could have a fuse blown somewhere
– user38183Oct 11 '18 at 10:00

2 Answers
2

It sounds like you've flattened your battery by listening to the radio without the engine running. If this was only a few minutes, it may be that your battery is in poor health and due for replacement anyway.

If you obtained a reading of 18 volts from your multimeter, I'd suggest replacing that too as a 12 volt battery should never produce such a high reading. Even with the engine running and the alternator acting I'd expect a maximum reading of less than 15 volts.

In the first instance, charge the battery and see if the car starts. You could also try jumping it from another vehicle or a charged jump pack but given the choice I'd personally want to charge the battery with a charger.

A dead battery was the first possibility I considered. However, the symptoms are quite inconsistent with a dead battery. Nevertheless, I did try to jump it, just in case, but without success. Finally, the battery is nearly new, so it's unlikely that anything is wrong with it. I don't know, however, whether the multimeter is in proper working order. If I can find my other one, I'll test with it.
– Scott SeveranceOct 11 '18 at 14:02

1

A discharged battery will frequently provide enough power to run things on the car such as interior lights but will appear completely dead when attempting to crank the starter motor. You'll also find a discharged but relatively healthy battery will regenerate some of its charge if left for a period of time. Other things to check are wiring connectors, earthing points and ignition switches.
– Steve MatthewsOct 11 '18 at 14:45

Yes, but a dead battery which still has enough power to run the lights will still run the lights after failing to crank the engine.
– Scott SeveranceOct 11 '18 at 14:48

1

No necessarily, I've seen discharged batteries provide ignition lights up until they're asked to crank the starter, then they provide nothing.
– Steve MatthewsOct 11 '18 at 14:49

I've edited the question as a result of testing with a different multimeter the upshot is I'm now measuring 12 volts across the battery terminals.
– Scott SeveranceOct 11 '18 at 18:12

It turns out that the problem was a bad connection between one of the battery cables and the connector which connects the cable to the terminal. Giving that connection a solid wiggle cured the problem.